Artificial posterior teeth

ABSTRACT

Artificial posterior cuspless teeth possess slightly convex functional occlusal surfaces in both mesiodistal and buccolingual directions on upper posterior teeth and slightly concave functional occlusal surfaces on lower posterior teeth, with both upper and lower posterior teeth configured to conform to the restored curves of Spee in an anterior-posterior direction and to conform to the restored curves of Wilson in a buccolingual direction.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation in part of U.S. patent applicationSer. No. 07/983,693 filed Dec. 1, 1992 and now U.S. Pat. No. 5,326,262.The entire disclosure of the above-listed prior co-pending applicationis hereby incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to artificial teeth, and more particularlypertains to improved artificial posterior teeth for use in cases wherethe patient is completely edentulous (without teeth) and especially incases where the edentulous ridges have been extensively resorbed or haveshrunk away.

2. Description of the Prior Art

A variety of methods, some of them drastic and involving surgery andimplants, have been developed to try to make dentures possessing greaterstability and retention. Such surgical and implant methods expose thepatient to risk and high costs.

The posterior teeth that are presently being used in dentures aregenerally cusped and designed to be set up in what is called a balancedocclusion. This means that a very accurate bite or centric occlusionmust be established in the production of the denture. In all cases, ifthere is any error in setting up these teeth or even a minor amount ofridge resorption after the dentures are inserted, cusp interference willset up lateral forces which will tend to dislodge the denture whenlateral or protrusive excursions are made.

The other most common type of posterior teeth presently used in denturesare those with flat occlusal surfaces known as zero degree teeth. Theseteeth are set up in a flat plane and as soon as the wearer of denturesmoves into lateral or protrusive excursions there is no balancingocclusion. In other words, the wearer loses contact of many opposingposterior teeth and destabilizing forces are the probable outcome.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide new andimproved artificial teeth which can be used to develop dentures whichpossess greater stability than any dentures presently available. It isbelieved that ill fitting and unstable dentures cause more rapidresorption of the dental ridges. Thus, the provision of more stabledentures will help maintain the ridges and therefore keep the edentulouspatient more dentally fit.

Additionally, dentures that are unstable and loosened during chewing aredifficult for the wearer to use and cause a great many sore spots forthe patient. A further object of the invention is to minimize suchpatient discomfort through the provision of more stable dentures.

Yet another object of the invention is the provision of improvedartificial posterior teeth suitable for use in implants, resulting inthe prevention of destabilizing forces and a concomitant reduction instress on the implant.

An additional object of the invention is the provision of artificialposterior cuspless teeth designed especially to prevent any instabilityto the denture, and to give maximum balanced occlusal contact in centricocclusion and all excursions.

Yet another further object of the invention is to allow for greatererror in the setting up of the teeth because a slight error in takingcentric relation is less likely to cause great problems as inconventional techniques employing cusped teeth. Cusps on teeth interferewith centric occlusion and lateral excursions very quickly if they arenot placed precisely where they should be. Because the technique of theinvention is less sensitive, it is believed that dentures can beproduced more easily and cheaply than prior art dentures. For the samereasons, a slight amount of resorption of the ridge will produce fewerproblems as compared with prior art dentures. Dentures producedaccording to the present invention will be more comfortable for thepatient to wear because they are designed to be stable and to stay inuniform contact throughout all excursions without any destabilizingforces. All forces applied from the lower denture to the upper denturewill tend to keep each denture stabilized in place. Fewer sore spotsafter inserting the dentures will result in fewer dental appointmentsbeing necessary.

In order to achieve these and other objects of the invention, thepresent invention provides improved cuspless artificial teeth whichinclude slightly convex functional occlusal surfaces in both mesiodistaland buccolingual directions on upper posterior teeth and slightlyconcave functional occlusal surfaces on lower posterior teeth, with bothupper and lower posterior teeth configured to conform to the restoredcurves of Spee in an anterior-posterior direction and to conform to therestored curves of Wilson in a buccolingual direction.

These and various other advantages and features of novelty whichcharacterize the invention are pointed out with particularity in theclaims annexed hereto and forming a part hereof. However, for a betterunderstanding of the invention, its advantages, and the objects obtainedby its use, reference should be made to the drawings which form afurther part hereof, and to the accompanying descriptive matter, inwhich there is illustrated and described preferred embodiments of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view illustrating a mandible with naturalteeth and depicting how a curve touching the tips of cusps of teethtends to form an arc known as "the curve of Spee".

FIG. 2 is a side elevational view illustrating how the mandibularartificial teeth of the present invention possess occlusal surfaces ofeach tooth which form a segment of the curve of Spee.

FIG. 3 is a frontal sectional view through the molars of upper and lowermodels of natural dentition depicting an arc described touching the tipsof the cusps in a buccolingual direction. This arc is known as the"curve of Wilson".

FIG. 4 is a frontal sectional view through the molars of an upper modelof dentition showing the occlusal surface of the upper teeth of thepresent invention to be segments of the curve of Wilson.

FIG. 5 is a frontal sectional view through the molars of a lower modelof dentition showing the occlusal surface of the lower teeth of thepresent invention to be segments of the curve of Wilson.

FIG. 6 is a frontal sectional view through the molars of a dentitionmodel which attempts to use a flat or zero degree tooth in the techniqueof the present invention.

FIG. 7 is a frontal sectional view through the molars of an upper modelof dentition employing artificial teeth according to the presentinvention and illustrating the substantially vertical buccal teethsurfaces and the very slightly convex occlusal teeth surfaces whichfollow the curve of Wilson.

FIG. 8 is a plan view illustrating an upper model of natural dentition.

FIG. 9 is a plan view illustrating a lower model of natural dentition.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Referring now to the drawings, wherein like reference numerals designatecorresponding structure throughout the views, and referring inparticular to FIG. 1, it will be noted that natural teeth T in a lowermandible M possess cusps C, the tips of which lie on an arc known in thedental field as "the curve of Spee".

As can be appreciated from the plan views of upper and lower models ofnatural dentition illustrated respectively in FIGS. 8 and 9, themesiodistal direction MD is defined by a line that follows the arch ofthe teeth from a median line L to the distal surface DS of the secondmolar. The occlusal surfaces OS of the teeth are the facing bitingsurfaces. The maxilla is the upper jaw, and the maxillary molars are theupper molars. The buccolingual direction BL (FIG. 9) is the directionfrom the cheek side of a tooth to the tongue side, and the buccal toothsurfaces BS are the side surfaces facing the cheek.

As shown in FIG. 2, the artificial posterior teeth, both upper andlower, according to the present invention form segments of the curve ofSpee in a mesiodistal direction on the occlusal surface. As a result,the teeth will slide freely in an anterior-posterior direction as themandible M moves forward or backward and will remain in contact withopposing teeth on both sides of the arch. The curvature (curve of Spee)is such that the most posterior teeth may be moving down and forward, asthe mandibular condyle MC does in a forward movement, while the moreforward of the posterior teeth may actually be moving forward and upwardand yet all teeth are still in full contact and all forces applied in anocclusal direction will be directed perpendicular to the curve of Spee.

FIG. 3 shows a frontal sectional view of natural dentition as well as aline called the "curve of Wilson". This curve is in a buccolingualdirection and is such that the surfaces OS of the mandibular molars MM(FIG. 9) direct forces outwardly against the mandible M while those ofthe maxillary molars direct forces inwardly against the maxilla MX. Thisis true even though natural teeth have cusps on them. This inventionproposes teeth which are segments of these arcs (curves of Wilson) onthe occlusal surfaces OS, but without having cusps on them (FIGS. 4 and5). This will allow teeth on the right side of the mandible to move tothe right and upward in a lateral excursion to the right while the leftside of the mandible M moves downward forward and to the right in thatsame excursion. At all times the upper and lower teeth will remain infull contact on both sides of the arch when occlusal pressure is appliedand there is no food in the mouth. Pressure applied in an occlusaldirection will then be applied perpendicular to the curves of Wilson ina buccolingual direction BL so that forces in the mandibular arch MA(FIG. 9) will be directed downward and outward and in the maxillary archMXA (FIG. 8) those forces will be directed in an upward and inwarddirection. The mandibular arch MA (FIG. 9) is generally larger than themaxillary arch MXA (FIG. 8) in that the ridge of the mandible isgenerally outside the ridge of the maxilla, i.e. buccally to it. Theforces applied to these teeth will therefore always tend to seat thedenture in all directions. Excursions of the mandible M to the oppositeside will react in a similar fashion.

What has been described is recognized as the simplest form of theocclusal surfaces OS of the teeth of this invention. In the simplestform, the occlusal surface OS of the upper molars MT and bicuspids BT(FIG. 8) would be slightly convex both mesiodistally MD andbuccolingually BL. The slopes of the occlusal surfaces OS from buccal tolingual will be downward following the restored curves of Wilson.

Because of esthetics and even chewing efficiency it may be better tomake adjustments and modifications to these occlusal surfaces to betterserve the patients using them. It would be better to make the teethappear as much like cusped teeth as possible for appearance and marginalridges would add to the function of the teeth. Other indentations in theocclusal surfaces may help both appearance and function. Therefore, itis suggested that the occlusal surfaces of these teeth be modified asmuch as possible for appearance and efficiency as long as the principlesoutlined above are followed: i.e. forces will at all times be directedperpendicular to the restored curves of Spee and Wilson when occlusalforces are applied and there is nothing between the teeth. The upper andlower teeth will also be designed to slide freely anteriorly andposteriorly as well as in lateral excursions without any interferencealong the restored curves of Wilson and Spee.

For the sake of simplicity the occlusal surfaces of the teeth in thisinvention have been described as following the restored curves of Speein a posterior anterior direction and of following the restored curvesof Wilson in a buccolingual direction. However, because of the movementsof the mandible and the slopes of the articular eminences it may turnout that the best occlusal curves for the teeth would be modifiedsomewhat. For the sake of simplicity it should be assumed that when theterms "restored curves of Spee and Wilson" are used that a bit ofmodification may be implied because of mandibular movements andtemporomandibular joints.

I have used zero degree teeth in trying to make dentures as outlinedabove, but theses teeth ideally should have a slightly convex surface onthe uppers and a slightly concave surface on the lowers for mytechnique. It has also been found that the occlusal surface OS of a flator zero degree tooth is horizontal in a buccolingual BL direction whenthe buccal surface BS of the tooth is in proper position for esthetics(FIG. 6 at A). In my technique, the occlusal surface OS of the toothslopes downward from buccal to lingual BL following the curve of Wilsonwhen the buccal surface BS is properly placed for esthetics. If the flattooth occlusal surface OS is aligned with the curve of Wilson as closeas possible, the slope of the buccal surface BS is inclined too farmedially in an occlusal to gingival direction (FIG. 6 at B). FIG. 7 at Aand B shows how these problems are corrected by the instant invention.

The curvatures in the arcs of the restored curves of Wilson and Speewill vary from patient to patient, depending upon the sizes of themaxillas and mandibles involved and also on their relationship to eachother. The curves which allow maximum contact of the occlusal surfaceswill also be affected by the shape and function of the temporomandibularjoint. The present invention provides artificial teeth which restore theocclusion for all these natural curves to give maximum balanced occlusalcontact in centric occlusion and all excursions.

It is proposed that the teeth should be manufactured in small, mediumand large sizes for different jaw sizes. Each jaw size should have teethmade in ten, twenty, thirty and forty degree variations. The degreesrepresent the angulation the curve of Wilson makes with a horizontalline. The teeth would be made so that their occlusal surface correspondsto the curvature of properly positioned corresponding sphericaltemplates of ten, twenty, thirty, and forty degrees. The proper positionof the templates is outlined below. This type of template has been usedin dentistry for many years.

In practice the models of the edentulous mouth are mounted on anarticulator in centric occlusion, and the anterior teeth are properlyset up in bite blocks which are on the models. An appropriate sphericaltemplate is then used to make the approximate curves of Spee and Wilsonin the lower bite block. This can be done by heating the template andmelting the wax on the lower bite block from the incisal tips of thelower cuspids to the proper height at the posterior ends of the lowerbite block. The proper posterior height is generally determined inrelation to the retromolar pads--pear shaped bodies at the posteriorends of the lower ridge. The posterior teeth, corresponding to thetemplate used, of both the upper and lower dentures are then set in waxto function with maximum occlusal contact along the curves of thetemplate as produced on the lower bite blocks. The teeth are set so thatthe bite must be closed about two millimeters to reach the correctvertical dimension.

After fully waxing up the dentures, the posterior teeth are placed in awarm water bath, and the wax is allowed to soften slightly around theteeth so that pressure on the teeth can cause them to move. The denturesare inserted and the patient is asked to gently move the mandibleforward and back and in all normal working excursions, using very slightpressure, until all the posterior teeth are in maximum contact, and thecorrect vertical dimension is reached.

This procedure allows teeth which were not in contact to come intocontact, and teeth which were prematurely contacting to move out untilall the teeth contact evenly. The form of the teeth of this invention issuch that they tend to line themselves up correctly along thefunctionally restored curves of Spee and Wilson for that patient. Minorvariations in anatomy and function are taken care of by the procedure.When the patient has the maximum contact of the posterior teeth in allworking positions of the mandible, at the correct vertical dimension,then for the purpose of this invention it is said that those teeth havebeen restored to the curves of Spee and Wilson for that patient.

At this point the buccal surface of the posterior teeth should be withinsix or seven degrees of proper vertical alignment in a buccolingualdirection. If the vertical alignment is out by more than six or sevendegrees, the wrong tooth has been used, and the procedure should berepeated with the correct tooth.

The teeth according to the present invention may be made of porcelain,plastic, metal, or other materials.

It is to be understood, however, that even though numerouscharacteristics and advantages of the present invention have been setforth in the foregoing description, together with details of thestructure and function of the invention, the disclosure is illustrativeonly, and changes may be made in detail, especially in matters of shape,size and arrangement of parts within the principles of the invention tothe full extent indicated by the broad general meaning of the terms inwhich the appended claims are expressed.

What is claimed is:
 1. Artificial cuspless posterior upper and lower teeth comprising functional occlusal surfaces configured to conform to the restored curves of Spee in an anterior posterior direction.
 2. Artificial cuspless posterior upper and lower teeth comprising functional occlusal surfaces configured to conform to the restored curves of Wilson in a buccolingual direction.
 3. Artificial cuspless posterior upper and lower teeth comprising functional occlusal surfaces configured to conform to the restored curves of Spee in an anterior posterior direction, and also configured to conform to the restored curves of Wilson in a buccolingual direction. 